The present invention relates generally to string trimmers and more particularly to lawn and garden trimming devices using a monofilament string as the cutting/trimming element, the monofilament being whirled at a rapid speed by its attachment to a rotating motor. The original device of the character to which this invention relates has been marketed for years under the registered trademark "Weedeater.RTM.", but other manufacturers now make and sell a variety of similar string trimmer type devices.
It will be appreciated by those skilled in the art that string trimmer devices generally employ a monofilament as the cutting element of the trimmer. The monofilament is made from a synthetic, often extruded, material. The monofilament is connected to the shaft of a motor and as the motor is activated, the shaft rotates at a high rate of speed causing the monofilament to whip about its axis and tear or shred anything in its path. In the normal case, only one end of the monofilament extends from the trimmer and as that end comes in contact with grass, weeds, the earth, sidewalks or the like in the course of its use, the end of the monofilament will tend to shred or tear. Thus, the end of the monofilament extending from the trimmer will become shorter and shorter with use until it is frayed to a point where little if any portion of the monofilament extends beyond the point where it is connected to the rotating shaft of the trimmer.
When the rotating monofilament frays to the point where there is little or no length to the end extending beyond the rotating shaft, the monofilament must then be lengthened. A variety of devices have been structured to facilitate this process. In its most rudimentary construction, the monofilament would be wound about the shaft of the motor or the housing connected to the shaft of the motor and the user of the trimmer would have to grip the end of the monofilament extending from the housing and manually pull it from the spool contained within the housing so as to lengthen the end of the monofilament. Improvements were developed so that the base of the housing of the carrier of the monofilament could be tapped on a surface such as the ground or sidewalk as the unit was rotating, and the mechanical gripping of the monofilament would be released and the centrifugal force of the turning of the device about the shaft would cause the end of the monofilament to extend from the housing and the duration and number of taps on the bottom of the trimmer would control the length to which the monofilament would extend beyond the housing.
The difficulty that has been observed by Applicant with the types of devices just described is that they are generally made of plastic or similar material and tapping the bottom of the trimmer will eventually result in the housing for the monofilament being cracked or broken. This is a particular problem in commercial usage of trimmers, and once the housing for the coil of monofilament is broken, it is difficult and expensive to replace. In addition, with only one end of the monofilament extending from the trimmer, the trimming process takes longer and the end of the monofilament is frayed and torn from the monofilament after only a short usage. Therefore, the user of the trimmer must continually extend the end of the monofilament by tapping the end of the trimmer onto the ground, a sidewalk or the like, thereby increasing the likelihood of destruction of the monofilament coil housing.
Considering these problems with the prior art devices, there is a need for a replacement head for string trimmers which overcomes the deficiencies of the prior art. Such a device is presently unavailable and does not appear to be suggested by the prior art.